Many industrial processes and operations require the use of automated equipment to maintain manufacturing efficiencies. Robots have long been used as an integral part of factory automation and the use thereof has increased substantially in the recent past. The growing sophistication of computer electronics has permitted robots to be utilized in increasing ways to perform tasks requiring a high level of sophistication and accuracy. The costs of the electronic systems has decreased dramatically and has therefore permitted robot use to increase. Unfortunately, the mechanical components of the robot have not decreased in cost and simplicity as much as the electronic components.
Prior art robots have been either very complicated sophisticated assemblies capable of extreme accuracies or relatively simple unsophisticated assemblies of much lower accuracy levels. Modern machine tools are capable of producing parts within extremely minute tolerances and, consequently, utilization of a robot in a machine tool system requires that the robot be extremely accurate. A robot utilized in a machine tool system must also be capable of accurately reproducing a particular set of movements if the machine tool is to be properly operated. Consequently, the robot, when utilized in a machine tool system, must include positive means for assuring proper placement and orientation of raw materials and finished products.
A further requirement is that the robot utilize simple mechanical systems which are not subject to a high probability of failure. Machine tool components are extremely reliable and the robot must therefore also be extremely reliable so as not to stop operation of the machine tool. As a consequence, the robot must be capable of being easily repaired and not require sophisticated maintenance procedures.
Finally, many machine tool users have limited free space. Successful utilization of a robot, therefore, requires that the robot not occupy an inordinate amount of space. Such a robot must, therefore, be compact in order to permit ready application to existing machine tool operations.
From the above, it can be seen that a robot suitable for use in a machine tool environment must be relatively inexpensive to manufacture, have a high degree of accuracy and require little floorspace. The ability to accurately and repeatedly position raw materials, such as round stock and the like, is of paramount importance. Additionally, the ability to accurately and repeatedly remove finished products from the machine tool and transport the finished product to a downstream processing operation is also necessary. The robot must be able to be programmed so as to perform various steps required in the machining of many parts. The disclosed invention provides such a robot and one which overcomes the limitations of the prior art.
Richter, U.S. Pat. No. 3,826,383, discloses an automatic handling apparatus wherein a robot manipulator is mounted to a rotatable base. The base is rotated through utilization of a V-belt which is driven by an electric motor. Such a system is relatively complicated and the accuracy and the speed of rotation are limited by the mass of the base and the attached manipulator. Additionally, V-belts are subject to stretching and therefore slippage on the sheeve. Consequently, the rotation system of Richter is not totally satisfactory for machine tool applications.
Ott, U.S. Pat. No. 3,522,838, discloses a diecasting extractor wherein the manipulator is rotated by means of a rack and pinion assembly. The rack is an integral part of the piston and the teeth of the rack are directly engaged with the teeth of the pinion. Consequently, displacement of the piston causes associated rotation of the manipulator. The rotation mechanism of Ott is not totally satisfactory because the rack operates directly on the pinion. Consequently, the inertia of the manipulator must be overcome by the cylinder and piston assembly if rotation is to be accomplished. Furthermore, rotation is a function both of the displacement of the piston and of the gear ratio between the rack and the pinion. Ott fails to disclose any mechanisms for positively assuring that the manipulator has rotated to the proper position. Consequently, accurate repeatability of rotation is not satisfactory.
Boyle, U.S. Pat. No. 3,954,188, discloses a universal transfer device wherein a robot manipulator is rotated by means of a chain drive system. Boyle further discloses the use of intermediate stops to provide stop positions as required. The stops are mounted on a stop plate and utilize threaded holes. It can be appreciated that the Boyle device is rather complicated. The chain is rotated by means of an hydraulic motor and the rotation thereof is susceptible to inaccuracies due to pressure fluctuations and the inertia of the manipulator. The utilization of an hydraulic system is also not totally satisfactory because of the operating pressures which are required. A similar system is disclosed in Shum, U.S. Pat. No. 4,392,776. Shum uses a chain drive mechanism and a rotary hydraulic motor to rotate the robot. As previously indicated, pressurized hydraulic systems are not totally satisfactory for various reasons.
In view of the above, it can be seen that none of these systems provides a totally satisfactory solution for a robot rotary drive mechanism which may be utilized in a machine tool environment. The above patents are all complicated systems which are susceptible to inaccurate positioning. These systems require sophisticated maintenance and are likely to break down more often than the machine tool which they service.